In our home we have TV over IP and our ISP ships special router with two Ethernet ports dedicated for the TV (they are not manageable by modem's administration interface). Each port supports only one TV set-top-box (only TV for short) and the TV has to be connected directly to the port. The router also has two ports for normal internet and WiFi.

For now we have four Powerline adaptors - two are connected to the dedicated TV ports and other two to the Televisions, each pair (modem-TV) runs different Powerline network. Other devices have to connect by WiFi since the router is too far away and there is no room for more Powerline adaptors, but wifi signal is weak (thick walls).

Is it possible to connect both TVs and some other computers to the same Powerline network and place something (switch?) between the Powerline adaptor and the router, which will route data based on MAC address?
It would be also nice to somehow direct all packets coming from dedicated ports to respectful TV MAC Address (by editing them), so that TVs don't get confused.

For example:
send data from TV1 to port 1 (dedicated for TV)
edit headers of all packets from port 1 to have TV1 Mac Address
send data from TV2 to port 2 (dedicated for TV)
edit headers of all packets from port 1 to have TV1 Mac Address
everything else to port 3 (internet) make sure nothing form port 3 is directed towards any TV

As I understand it, switches keep table of MAC addresses and send packets to the interface where desired address is located. Therefore I will probably need a router... However I suspect the fact that two devices will be connected with multiple Ethernet cables will cause problems.

Is it possible? Can it be easily done? If so, will it be cheap (max. $100)?


If I have the post deciphered right, sounds like you want to have multiple separate "networks" over the same wire.

While this depends on how exactly those TV-specific ports were configured, you should be able to use a VLAN-capable switch with them.

  • Research: Open Wireshark on a computer, let it monitor Ethernet, then connect the computer either directly to the TV itself, or maybe to one of the modem's TV-specific ports. Watch the packets received by Wireshark. In their "details" view, check if there's an "802.1Q Virtual LAN" header below "Ethernet II".

  • If the TVs already use VLANs, it'll need more hackery than I can offer – see if someone else can suggest something better. I guess switches supporting QinQ could deal with that in a manner similar to below...

  • But if the TV traffic doesn't use VLANs yet, you can use them instead, to keep their traffic separate.

    Obtain two switches with VLAN tagging (802.1Q) support. (It's a feature in nearly all 'smart' and 'managed' switches. Even some "wireless routers" can be repurposed for this, if the firmware allows it.) In both, configure three ports as such (with "PVID" sometimes labelled "incoming" or "default VLAN", and the others labelled as "outgoing"... it varies):

    1. Powerline – PVID 1, VLANs 1 [untagged], 10 [tagged], 20 [tagged]
    2. First TV – PVID 10, VLAN 10 [untagged]
    3. Second TV – PVID 20, VLAN 20 [untagged]
  • This way, any packets entering the "first TV" port will be tagged with "VLAN 10" based on the port's PVID, and then they'll exit through the "powerline" port with the tag still on. The other switch receiving them will recognize the tag, and only allow the packet to exit through the same "first TV" port.

    (This doesn't involve any "editing of MAC addresses". I do not see why that would ever be required.)

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  • Thank you, @grawity. I used Wireshark and detected no VLAN. The router just spewed out Megabytes of video and IGMP packets. The set-top-box just sent DHCP requests. The VLAN will be possible, but costly. I hoped it would be solvable with only one device. – andowero Aug 27 '16 at 12:50

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